There has previously been described in previous U.S. patent application Ser. No. 09/719,136 (filed on Apr. 4, 2001 and published as International Publication WO 99/64218 on Dec. 16, 1999), an arrangement in which there is a chamber within a mold which is partially filled with a liquid and a remainder of the chamber is filled substantially only with the vapour of the liquid.
There is arranged a condensing arrangement positioned above a level of liquid in the chamber in relation to a source of heat within the chamber so as to cool and condense thereby vapour formed as a result of conversion from the liquid from the source of heat.
This arrangement has been found to have significant advantages in keeping temperatures of portions of the mold at relatively similar temperatures and therefore those parts of the mold that are used for defining the shape of a molded article and are required to be cooled from time to time to assist in the cyclic use of the mold. Such an arrangement can keep the mold at a more uniform and even temperature through its usage cycles.
One of the problems encountered has been that the head of any liquid within the chamber causes the liquid at a deepest point within a body of the liquid to be implicitly under a higher pressure and therefore the liquid at greater depth will “boil” at a higher temperature than the liquid at lesser depth. This then will result in temperature differences where it would be better if these differences were not so large.
Generally it is an object of this invention to provide improvements to assist in keeping more uniform temperatures in a mold using this general concept or at the least providing the public with a useful improvement in relation to molds.